Effect of neuromuscular blockers and opiates on the cerebrovascular response to endotracheal suctioning in adults with severe head injuries

BACKGROUND: Intracranial hypertension occurs in response to routine procedures such as endotracheal suctioning in patients with severe head injuries. In some patients, the intracranial pressure does not immediately return to baseline levels. OBJECTIVES: To examine the effect of drug administration on cerebrovascular response to endotracheal suctioning in adults with severe head injuries. METHODS: Seventy-one subjects were divided into 3 groups: those who received no drugs, those treated with opiates only (morphine sulfate and fentanyl citrate), and those treated with a neuromuscular blocking agent (vecuronium bromide) plus opiates. A controlled protocol involving 2 sequences of endotracheal suctioning that included hyperoxygenation, hyperinflation, and suctioning was used for all subjects. Two-way repeated-measures analyses of variance were done with type of drug as the between-subject factor and phase of suctioning as the within-subject factor. Survival analysis was used to compare the return of intracranial pressure to baseline levels among the 3 groups. RESULTS: Changes in intracranial pressure were significantly smaller in subjects who received a neuromuscular blocking agent plus opiates than in subjects who did not receive any drugs or received opiates only. The greatest increase in intracranial pressure from baseline was in the first and second phases of suctioning. The 3 groups showed no significant difference in the return of intracranial pressure to baseline level. CONCLUSIONS: Neuromuscular blockers attenuate the increases in intracranial pressure that occur with endotracheal suctioning. It is not known whether control of procedurally induced elevations in intracranial pressure affects long-term outcomes in adults with severe head injuries.

Variation in the diagnosis of upper respiratory tract infections and otitis media in an urgent medical care practice

BACKGROUND

Variation among hospitalized medical conditions have been reported previously, but there is little information on variation among physicians for medical conditions that constitute a substantial part of ambulatory care.

OBJECTIVE

To measure variation in the diagnosis of 2 common medical conditions, otitis media (OM) and upper respiratory tract infections (URIs) in an urgent care practice.

DESIGN

Estimate the variation in the incidence of new diagnoses of OM and URIs among 19 physicians working at 2 urgent care clinics between January 1, 1995, and March 31, 1995. Patients are seen in order of arrival, and assignment to each physician is random.

PARTICIPANTS AND SETTING

Two urgent care clinics staffed by the same 19 physicians. During the 3-month study period, 21,259 patients were seen at the 2 clinics; of these, 1839 (8.65%) received a diagnosis of first time OM; and 8020 (37.73%), of an URI.

MAIN OUTCOME MEASURE

Incidence of new diagnoses of OM and URI estimated as a proportion of all diagnoses for each individual physician.

RESULTS

There was substantial variation between physicians in the diagnosis of OM, ranging from a low of 4.2% to a high of 21.8%. There was less variation in the diagnosis of URI (31.7%-48.4%). Some physicians with a low incidence of OM or URI diagnoses had increased the proportion of diagnoses in the other diagnostic category. For OM the variation was greatest for children younger than age 5 years, but substantial variation was also found in adults. For URIs the variation was more uniform across all age groups. The variation was not explained by type of specialty training or years in medical practice.

CONCLUSIONS

There is substantial variation between physicians in their diagnosis of OM and URI in an urgent care setting. This variation has implications for cost of diagnosing and treating these conditions, the training of physicians, and our understanding of the treatment of OM.

Transcriptional repression by UME6 involves deacetylation of lysine 5 of histone H4 by RPD3

The histone deacetylase RPD3 can be targeted to certain genes through its interaction with DNA-binding regulatory proteins. RPD3 can then repress gene transcription. In the yeast Saccharomyces cerevisiae, association of RPD3 with the transcriptional repressors SIN3 and UME6 results in repression of reporter genes containing the UME6-binding site. RPD3 can deacetylate all histone H4 acetylation sites in cell extracts. However, it is unknown how H4 proteins located at genes near UME6-binding sites are affected, nor whether the effect of RPD3 is localized to the promoter regions. Here we study the mechanism by which RPD3 represses gene activity by examining the acetylation state of histone proteins at UME6-regulated genes. We used antibodies specific for individual acetylation sites in H4 to immunoprecipitate chromatin fragments. A deletion of RPD3 or SIN3, but not of the related histone-deacetylase gene HDA1, results in increased acetylation of the lysine 5 residue of H4 in the promoters of the UME6-regulated INO1, IME2 and SPO13 genes. As increased acetylation of this residue is not merely a consequence of gene transcription, acetylation of this site may be essential for regulating gene activity.

Special care units for people with Alzheimer's disease. Only for the privileged few?

The number of Special Care Units (SCUs) for people with Alzheimer's disease (AD) in nursing homes have increased dramatically in the past 10 years. Despite the rapid increase in number of SCUs and the concern that most SCUs report higher costs than traditional nursing home units where residents with AD are integrated with cognitively intact residents, the evaluation of costs has been largely unsystematic and noncomparative. Studies are urgently needed to assess comparative costs so that administrators and policy makers can make informed decisions. This article reviews studies that examine the costs of care in SCUs and presents cost-related data comparing the outcomes of care for residents with AD on a SCU and on traditional units in one long-term care setting.

Flow cytometric analysis of cellular changes in mice after intradermal inoculation with a liposome-iscom adjuvanted vaccine

As it is not known what changes to leucocyte homeostasis are mandatory for effective adjuvant action, the biological relevance of systemic changes elicited by different vaccine formulations can only be interpreted in the context of the immunological outcomes. We used flow cytometry to quantify the changes in leucocyte subsets induced in mice intradermally immunized with SAMA4 (adjuvant group), outer membrane proteins (OMP) purified from Actinobacillus pleuropneumoniae (OMP antigen group), SAMA4 adjuvanted OMP (OMP vaccine group), or phosphate-buffered saline (PBS: control group). This approach allowed direct comparisons to be made between the effects of antigen, adjuvant or antigen-adjuvant complexes on immune effector cell populations. Antigens complexed with the liposome-iscom hybrid adjuvant, SAMA4, generated strong antibody responses and cytotoxic T-cell activity in animals immunized intradermally, reflecting remobilization and recruitment of specific cell populations. Splenomegaly, due to granulocytosis, monocytosis and megakaryocytosis, was most prominent in the OMP vaccine group. Histological examination of spleen sections confirmed that these changes were due primarily to splenic haematopoiesis. Circulating numbers of granulocytes and monocytes increased significantly (P < 0.05) in the blood of the OMP vaccine group, as did granulocyte numbers in the lungs (P < 0.05). No changes in T- and B-cell numbers were detected by flow cytometry in the spleens, lungs or blood over the 28-day period in any treatment group. Thymocyte numbers (predominantly CD4+CD8+ cells) in the OMP vaccine group fell by 95% within 3 days of immunization. Identical cellular responses were obtained when an innocuous antigen, ovalbumin, was complexed with SAMA4 instead of OMP, thus demonstrating that the adjuvant effects of SAMA4 were due to synergistic interaction between antigen and adjuvant and not due to the presence of toxic components. The association of strong adaptive immune responses with such complex changes in leucocyte homeostasis induced by complexing adjuvant and antigen suggested that the changes were important for effective vaccination and were not purely circumstantial.

Distinctive patterns of histone H4 acetylation are associated with defined sequence elements within both heterochromatic and euchromatic regions of the human genome

The pattern of histone H4 acetylation in different genomic regions has been investigated by immunoprecipitating oligonucleosomes from a human lymphoblastoid cell line with antibodies to H4 acetylated at lysines 5, 8, 12 or 16. DNA from antibody-bound or unbound chromatin was assayed by slot blotting. Pol I and pol II transcribed genes located in euchromatin were shown to have levels of H4 acetylation at lysines 5, 8 and 12 equivalent to those in input chromatin, but to be slightly enriched in H4 acetylated at lysine 16. In no case did the acetylation level correlate with actual or potential transcriptional activity. All acetylated histone H4 isoforms were depleted in non-coding, simple repeat DNA in heterochromatin, though the extent of depletion varied with the type of heterochromatin and with the isoform. Two single copy genes that map within or adjacent to blocks of paracentric heterochromatin are depleted in H4 acetylated at lysines 5, 8 and 12, but not 16. Consensus sequences of repetitive elements of the Alu family (SINES, enriched in R bands) were associated with H4 that was more highly acetylated at all four lysines than input chromatin, while H4 associated with Kpn I elements (LINES, enriched in G bands) was significantly underacetylated.

The Fluctuating Abundance of Endangered Mammals on Bernier And Dorre Islands, Western Australia - Conservation Implications

Bernier and Dorre Islands in Shark Bay, Western Australia, provide refuge to populations of five species of threatened mammals that are extinct on the mainland other than as reintroduced or captive populations. This paper provides estimates of changes in population size of four species over three years from 1988-9 to 1991-2. The period from November 1986 to March 1989 was one of below average rainfall intensifying to severe drought on the islands; the period from mid 1989 to 1992 was one of average to above-average rainfall. Three of the four species (L. hirsutus, B. lesueur and P. bougainville) showed substantial and significant increases and one species (L. fasciatus) showed a small but non-significant increase in abundance. Combined estimates of minimum population size for both islands in 1991-2 vary from c. 4,000 P. bougainville to c. 10,000 L. fasciatus. If these densities are regarded as typical of average rainfall years then the drought in the late 1980s reduced populations of P. bougainville by up to 75%, B. lesueur by 65%, and L. hirsutus by up to 60%. Combined estimates for the four species give densities for the community of medium-sized mammals which vary between 160 km-2 in drought and 260 km-2 in years of average to above average rainfall.

Histone acetylation as an epigenetic determinant of long-term transcriptional competence

All four histones of the nucleosome core particle are subject to post-translational acetylation of selected lysine residues in their amino-terminal domains. The modification is ubiquitous and frequent. Steady-state levels of acetylation have been shown to vary from one part of the genome to another and to be maintained by a dynamic balance between the activities of two enzyme families, the histone acetyltransferases (HATs) and deacetylases (HDAs). The recent demonstration that some at least of these enzymes are homologous to, or identical with, known regulators of transcription, has renewed interest in the involvement of histone acetylation in transcriptional control. Acetylation might influence the initiation and/or elongation phases of transcription in a chromatin context, possibly by regulating the accessibility of nucleosomal DNA to transcription factors or the displacement of histones by the progressing transcription complex. But there is also evidence to suggest that acetylation might be involved in the longer-term regulation of transcription, acting as a marker by which states of genetic activity or inactivity are maintained from one cell generation to the next. This review outlines the evidence for such a role, using centric heterochromatin and the dosage-compensated male X chromosome in Drosophila as model systems, and suggests possible mechanisms by which it might operate.

Transient inhibition of histone deacetylation alters the structural and functional imprint at fission yeast centromeres

Histone acetylation may act to mark and maintain transcriptionally active or inactive chromosomal domains through the cell cycle and in different lineages. A novel role for histone acetylation in centromere regulation has been identified. Exposure of fission yeast cells to TSA, a specific inhibitor of histone deacetylase, interferes with repression of marker genes in centromeric heterochromatin, causes chromosome loss, and disrupts the localization of Swi6p, a component of centromeric heterochromatin. Transient TSA treatment induces a heritable hyperacetylated state in centromeric chromatin that is propagated in lineages in the absence of drug. This state is linked in cis to the treated centromere locus and correlates with inheritance of functionally defective centromeres and persistent chromosome segregation problems. Thus, assembly of fully functional centromeres is partly imprinted in the underacetylated or transcriptionally silent state of centromeric chromatin.

Histone underacetylation is an ancient component of mammalian X chromosome inactivation

Underacetylation of histone H4 is thought to be involved in the molecular mechanism of mammalian X chromosome inactivation, which is an important model system for large-scale genetic control in eukaryotes. However, it has not been established whether histone underacetylation plays a critical role in the multistep inactivation pathway. Here we demonstrate differential histone H4 acetylation between the X chromosomes of a female marsupial, Macropus eugenii. Histone underacetylation is the only molecular aspect of X inactivation known to be shared by marsupial and eutherian mammals. Its strong evolutionary conservation implies that, unlike DNA methylation, histone underacetylation was a feature of dosage compensation in a common mammalian ancestor, and is therefore likely to play a central role in X chromosome inactivation in all mammals.

Stage-dependent redistributions of acetylated histones in nuclei of the early preimplantation mouse embryo

In the preimplantation mouse embryo, activation of the embryonic genome is accompanied by a transient enrichment of histone H4 acetylated at lysines 5, 8, and 12 at the nuclear periphery (Worrad et al., 1995: Development 121:2949-2959). In the present report, we use laser-scanning confocal microscopy and a new panel of antibodies to define the distribution of specific acetylated isoforms of the other three core histones in mouse embryos at the 1- to 4-cell stage. We find that histone H3 acetylated at lysine 9 and/or 18 (H3.Ac9/18) and the single acetylated form of H2A (H2A.Ac5) become transiently enriched at the nuclear periphery in the 2-cell embryo. In contrast, H3.Ac14, H3.Ac23, and acetylated H2B, like H4.Ac16, remain distributed throughout the nucleoplasm. The staining intensity with antisera to H3.Ac9/18, even at the periphery was weak compared to that obtained with antisera to acetylated H4. A brief period of culture, however, in the presence of the inhibitor of histone deacetylases trichostatin A (TSA) or trapoxin increased labeling. Thus, the steady-state level of H3.Ac9/18 at the nuclear periphery and H3.Ac14 and H3.Ac23 in the nuclear interior is relatively low, but turnover remains high. The localization of selected acetylated isoforms of H3 and H2A at the nuclear periphery was independent of ongoing transcription or of cytokinesis, but did require DNA replication. We propose a model in which the selective, replication-dependent acetylation and deacetylation of zygotic chromatin at the nuclear periphery mediates the programming of zygotic transcription.

Different strategies of X-inactivation in germinal and somatic cells: histone H4 underacetylation does not mark the inactive X chromosome in the mouse male germline

It has previously been shown by immunocytochemistry that the inactive X chromosome (Xi) in somatic cells of human and mouse females is marked by underacetylation of histone H4. It has been suggested that this may be important for transcriptional silencing of genes on Xi. We have now investigated X-inactivation in meiotic cells of the male germline. In these cells the single X chromosome is transcriptionally inactive and expresses XIST, a gene that in somatic cells is transcribed only from Xi. By immunostaining with antibodies to H4 acetylated at lysines 5, 8, 12, or 16, we demonstrate that histone H4 on the male X is not underacetylated. We conclude that there is a differential germline strategy for maintenance of X-inactivation and that H4 underacetylation, though associated with the long-term marking of inactive X chromosomes in the female soma, is not always essential for the transcriptional down-regulation of X-linked genes.

X-Inactivation and histone H4 acetylation in embryonic stem cells

In female mammalian cells, dosage compensation for X-linked genes is achieved by the transcriptional silencing, early in development, of many genes on just one of the two X chromosomes. Several properties distinguish the inactive X (Xi) from its active counterpart (Xa). These include expression of Xist, a gene located in the X-inactivation center (Xic), late replication, differential methylation of selected CpG islands and underacetylation of histone H4. The relationship between these properties and transcriptional silencing remains unclear. Female mouse embryonic stem (ES) cells have two active X chromosomes, one of which is inactivated as cells differentiate in culture. We describe here the use of these cells in studying the sequence of events leading to X-inactivation. By immunofluorescent labeling of metaphase chromosome spreads from ES cells with antibodies to acetylated H4, we show that an underacetylated X chromosome appears only after 4 days of differentiation, and only in female cells. The frequency of cells with an underacetylated X reaches a maximum by Day 6. In undifferentiated cells, H4 in centric heterochromatin is acetylated to the same extent as that in euchromatin but has become relatively underacetylated, as in adult cells, by Day 4 of differentiation (i.e. , when deacetylation of Xi is first seen). The overall deacetylation of Xi follows Xist expression and the first appearance of a single, late-replicating X, both of which occur on Day 2. It also follows the silencing of X-linked genes. Levels of mRNA from four such genes, Hprt, G6pd, Rps4, and Pgk-1, had all fallen by approximately 50% (relative to the autosomal gene Aprt) by Days 2-4. The results show that properties that characterize Xi are put in place in a set order over several days. H4 deacetylation occupies a defined place within this sequence, suggesting that it is an intrinsic part of the X-inactivation process. The stage at which a completely deacetylated Xi is first seen suggests that deacetylation may be necessary for the maintenance of silencing but is not required for its initiation. Nor is it required for, or an immediate consequence of, late replication. However, we note that selective deacetylation of H4 on specific genes would not be detected by the microscopical approach we have used and that such selective deacetylation may still be part of the silencing process.

HDA1 and RPD3 are members of distinct yeast histone deacetylase complexes that regulate silencing and transcription

Increased histone acetylation has been correlated with increased transcription, and regions of heterochromatin are generally hypoacetylated. In investigating the cause-and-effect relationship between histone acetylation and gene activity, we have characterized two yeast histone deacetylase complexes. Histone deacetylase-A (HDA) is an approximately 350-kDa complex that is highly sensitive to the deacetylase inhibitor trichostatin A. Histone deacetylase-B (HDB) is an approximately 600-kDa complex that is much less sensitive to trichostatin A. The HDA1 protein (a subunit of the HDA activity) shares sequence similarity to RPD3, a factor required for optimal transcription of certain yeast genes. RPD3 is associated with the HDB activity. HDA1 also shares similarity to three new open reading frames in yeast, designated HOS1, HOS2, and HOS3. We find that both hda1 and rpd3 deletions increase acetylation levels in vivo at all sites examined in both core histones H3 and H4, with rpd3 deletions having a greater impact on histone H4 lysine positions 5 and 12. Surprisingly, both hda1 and rpd3 deletions increase repression at telomeric loci, which resemble heterochromatin with rpd3 having a greater effect. In addition, rpd3 deletions retard full induction of the PHO5 promoter fused to the reporter lacZ. These data demonstrate that histone acetylation state has a role in regulating both heterochromatic silencing and regulated gene expression.

A collaborative international nursing informatics research project: predicting ARDS risk in critically ill patients

An international nursing informatics research collaboration between Duke University Medical Center in Durham, North Carolina, USA and Allgemeine Krankenhaus Hospital in Vienna, Austria used data mining techniques called Knowledge Discovery in Databases (KDD) to explore the relationship between clinical data variables and adult respiratory distress syndrome (ARDS) in critically ill patients. Results of the study and logistics of international research collaboration will be presented at NI '97. The conceptual model, data mining methodology, and objectives for the collaboration are described here.

Tomographic distribution of acetylated histone H4 in plant chromosomes, nuclei and nucleoli

Root tip cells of broad bean (Vicia faba L. cv. 'Wase soramame') and barley (Hordeum vulgare L. cv. 'Minorimugi') were immunostained with antibodies specific for acetylated histone H4. With an antiserum that recognizes histone H4 acetylated at lysine-5, the nucleolar organizing region (NOR) in mitotic chromosomes was strongly labeled in both species. The broad bean had two signals in the metaphase and telophase chromosome complements and four signals in the prophase and anaphase chromosome complements, while the barley had four signals in the metaphase and telophase chromosome complements and eight signals in the prophase and anaphase complements. Five different patterns of signals were observed at interphase: in type I only nucleoli were wholly stained; in type II perinucleolar knob-like signals and/or fiber-like signals emanated from the nucleus; in type III aggregate signals appeared in the nucleolus; in type IV many small dot-like signals were distributed throughout the nucleus, except nucleoli; and in type V string-like or some granule-like signals appeared in the nucleoli. Type II was very similar to previous results by in situ hybridization with sense rDNA probes. Type III was similar to the patterns of DNA synthesis recognized as chromatin domains by anti-BrdU antibodies. Type V was very similar to the results of in situ hybridization with pTa71, rDNA probes and the appearance of the dense fibrillar components of the nucleolus.

The pattern of histone H4 acetylation on the X chromosome during spermatogenesis of the desert locust Schistocerca gregaria

We have used antibodies directed against histone H4 acetylated at lysine residue 5, 8, 12, or 16 and indirect immunofluorescence microscopy to probe chromosomes from spermatogonia and spermatocytes of the desert locust, Schistocerca gregaria. The autosomes showed bright overall fluorescence, indicative of high levels of H4 acetylation. In contrast, the X chromosome, which is facultatively heterochromatic during spermatogenesis of the locust, remained completely unstained in spermatogonia and secondary spermatocytes and showed only a small terminal fluorescent band in primary spermatocytes. This band probably corresponds to centromere associated constitutive heterochromatin. Thus, underacetylation is a cytogenetic marker for facultative heterochromatin, but not necessarily constitutive heterochromatin, during spermatogenesis of the locust. Scanning electron microscopy of chromosomes from prophase spermatogonia and prophase I spermatocytes revealed that underacetylation of histone H4 in the X chromosome was not accompanied by a chromatin organization visibly different from that of the autosomes. Transmission electron microscopy of mitotic spermatogonia showed that the X chromosome is separated from the autosomes in a small nuclear compartment of its own in prophase and telophase and associated with membranes in metaphase. In prophase I spermatocytes, autosomes and the sex univalent were in the same compartment. This compartmentalization may be responsible for the underacetylation and (or) transcriptional silencing of the X chromosome in spermatogonia mitosis.

Acute angle closure glaucoma masquerading as systemic illness

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Efficient transcriptional silencing in Saccharomyces cerevisiae requires a heterochromatin histone acetylation pattern

Heterochromatin in metazoans induces transcriptional silencing, as exemplified by position effect variegation in Drosophila melanogaster and X-chromosome inactivation in mammals. Heterochromatic DNA is packaged in nucleosomes that are distinct in their acetylation pattern from those present in euchromatin, although the role these differences play in the structure of heterochromatin or in the effects of heterochromatin on transcriptional activity is unclear. Here we report that, as observed in the facultative heterochromatin of the inactive X chromosome in female mammalian cells, histones H3 and H4 in chromatin spanning the transcriptionally silenced mating-type cassettes of the yeast Saccharomyces cerevisiae are hypoacetylated relative to histones H3 and H4 of transcriptionally active regions of the genome. By immunoprecipitation of chromatin fragments with antibodies specific for H4 acetylated at particular lysine residues, we found that only three of the four lysine residues in the amino-terminal domain of histone H4 spanning the silent cassettes are hypoacetylated. Lysine 12 shows significant acetylation levels. This is identical to the pattern of histone H4 acetylation observed in centric heterochromatin of D. melanogaster. These two observations provide additional evidence that the silent cassettes are encompassed in the yeast equivalent of metazoan heterochromatin. Further, mutational analysis of the amino-terminal domain of histone H4 in S. cerevisiae demonstrated that this observed pattern of histone H4 acetylation is required for transcriptional silencing. This result, in conjunction with prior mutational analyses of yeast histones H3 and H4, indicates that the particular pattern of nucleosome acetylation found in heterochromatin is required for its effects on transcription and is not simply a side effect of heterochromatin formation.

Histone H4 acetylation and replication timing in Chinese hamster chromosomes

The distribution of acetylated isoforms of histone H4 along Chinese hamster chromosomes has been studied by immunostaining with antibodies recognizing H4 acetylated at defined lysines in its N-terminal domain. The heterochromatic long arm of the X chromosome in both female (CHO) and male (DON) cell lines is underacetylated at three out of four lysines (5, 8, and 12). In contrast, the level of acetylation at lysine 16, which is the first to be acetylated in mammals, was similar in X chromosomes and autosomes. Labeling of the cells with bromodeoxyuridine (BrdU) to mark late-replicating chromosome domains, followed by double immunostaining with antibodies to BrdU and acetylated H4, showed a close, though not perfect, correlation between late replication and low levels of H4 acetylation. The results show that levels of histone acetylation are associated with the replication timing of defined domains on both the X chromosome and autosomes, but the exceptions we observe suggest that this link is not absolute or essential.

Differential underacetylation of histones H2A, H3 and H4 on the inactive X chromosome in human female cells

It has previously been shown that the acetylated forms of histone H4 are depleted or absent in both constitutive, centric heterochromatin and in the facultative heterochromatin of the inactive X chromosome (Xi) in female cells. By immunostaining of metaphase chromosomes from human lymphocytes with antibodies to the acetylated isoforms of histones H2A and H3, we now show that these histones too are underacetylated in both Xi and centric heterochromatin. Xi shows two prominent regions of residual H3 acetylation, one encompassing the pseudoautosomal region at the end of the short arm and one at about Xq22. Both these regions have been shown previously to be sites of residual H4 acetylation. H2A acetylation on Xi is higher overall than that of H3 or H4 and is particularly high around the pseudoautosomal region, but not at Xq22. The results suggest that the acetylated isoforms of H3 and H4 have at least some effects on chromosomal structure and function that are not shared by acetylated H2A.